org 0x7c00
[bits 16]
xor ax, ax ; eax = 0
; 初始化段寄存器, 段地址全部设为0
mov ds, ax
mov ss, ax
mov es, ax
mov fs, ax
mov gs, ax
mov dl,0  
;mov dh,8
mov bl,0x75 ;白底红字
mov cx,1

; 初始化栈指针
mov sp, 0x7c00
mov bh,0x00   ;页码为0

in:
mov ah, 0
int 0x16

out:
mov ah,0x02
inc dl
int 0x10

mov ah, 0x09
int 0x10

jmp in

jmp $ ; 死循环

times 510 - ($ - $$) db 0
db 0x55, 0xaa